Process of reducing deposition of deposits on heat exchange surfaces in petroleum refinery operations



United States Patent PROCESS OF REDUCING DEPOSITION OF DE- POSITS ONHEAT EXCHANGE SURFACES IN PETROLEUM REFINERY OPERATIONS Eugene A. Kent,Naperville, IlL, assignor to Nalco Chemical Company, Chicago, 111., acorporation of Delaware No Drawing. Filed Jan. 12, 1962, Ser. No.166,447 5 Claims. (Cl. 20848) This application is a continuation-in-partof my copending application, Serial No. 788,727, filed January 26, 1959,now abandoned.

This invention, in general, relates to a method of inhibiting depositionof organic substances on heated metal surfaces and has particularreference to the prevention of deposits on heated metal surfaces in heatexchangers or the like in the processing of petroleum hydrocarbons. Oneimportant aspect of the invention relates to the processing of petroleumhydrocarbon liquids under conditions of high temperatures and theprevention of organic deposits from said petroleum hydrocarbon liquidson heat exchange surfaces.

In the processing of hydrocarbon liquids, particularly petroleumhydrocarbon liquids, elevated temperatures are often used in manynecessary and important production operations. To handle liquids atelevated temperatures, heat exchangers and like heating devices areemployed to control the heat transfer from one operational step toanother. When hydrocarbon liquids contact hot metal surfaces there issome tendency for the liquid to decompose or undergo a chemical reactionthat manifests itself in the form of deposits. These deposits may beeither coke-like, or they may be in the form of tenacious, soft, stickysludges. In the first instance, the deposits maybe considered aspyrolytic decomposition products whereas in the second type they may beconsidered an oxidation products and/ or polymerizate compositions.

In either of the above cases the deposits tend to materially decreasethe heat transfer capacity of the metal surfaces and, hence, increaseoperating expenses. These deposits also require additional efiort andtime to remove and restore the equipment to its original operatingefficiency.

There are many petroleum refinery operations which can be benefited bythe reduction or prevention of the deposit tendencies of the particularpetroleum liquid being treated. For example, the reduction or preventionof deposits in heat exchange equipment, such as preheaters, heatexchange apparatus and the like, is important in such petroleum refiningoperations as cracking, hydroforming, desulfurization, reforming,distillation, absorption, isomerization, thermal desalting andextraction, to name a few. Deposits have been observed to form on heattransfer surfaces at temperatures as low as about 225 F. and may beevidenced at temperatures as extreme as 800 F. and perhaps higher.

One of the most convenient ways of preventing or reducing hightemperature organic deposits on heat exchange surfaces is to add a smallamount of a deposit-inhibiting or anti-fouling chemical to thehydrocarbon liquid which tends to form high temperature deposits. It is,therefore, an object of the present invention to reduce or prevent theformation of high temperature carbonaceous deposits on heat exchangesurfaces by chemical means.

Another object of the invention is to provide a chemical which whenadded to a hydrocarbon liquid will prevent the deposit-formingtendencies of said liquid when it contacts the exchange surfaces held atelevated temperatures.

In accomplishing these objects in accordance with the invention it hasbeen found that new and improved results in inhibiting the formation oforganic deposits from petroleum hydrocarbon liquids during theprocessing thereof at elevated temperatures, particularly attemperatures within the range of about 225 F. to 800 F., are obtained byadding, preferably by dissolving, in the hydrocarbon liquid a reactionproduct obtained by reacting at elevated temperatures in aliphaticpolycarboxy acid, a monohydroxy, monocarboxylic aliphatic acid, apolyhydroxy, polycarboxylic aliphatic acid, a monohydroxy,polycarboxylic aliphatic acid, or a polyhydroxy, monocarboxylic acid,preferably citric acid, and tetiary-alkyl primary amines. Thetertiary-alkyl primary amines have the formula:

it. the amine having 11-22 carbonsthe reaction being carried out withthe removal of 0.5-3.0 mols of the water of reaction per mol of thecitric acid. More specifically, the tertiary-alkyl primary amineconstitutes a compound wherein R and R are lower alkyl groups, usuallymethyl groups, and R constitutes a long chain alkyl radical composed of8 to 19 carbons. Tertiary-alkyl primary amines which have been found tobe eminently suitable for the instant invention are Primene Sl-R andPrimene JM-T. Primene 81-R is reported by its manufacturer to becomposed of principally tertiary-alkyl primary amines having 11-14carbons and has a molecular weight principally in the range of 171-213,a specific gravity at 25 C. of 0.813, a refractive index of 1.423 at 25C., and a neutralization equivalent of 191. Primene JM-T is reported bythe manufacturer to be composed of tertiary-alkyl pri- -mary amineshaving 18-22 carbons with a molecular weight principally in the range of2694125, a specific gravity at 25 C. of 0.840, a refractive index of 25C. of lt456, and a neutralization equivalent of 315. Of the two amines,Primene J M-T is preferred because the ultimate reaction products withcitric acid have better oil solubility as compared with equivalentproducts made with Primene 81-R.

The primary constituent of Primene 81-R is reported to be The primaryconstituent of Primene JM-T is reported to be essentially the samestructure of Primene 81-R, but with 22 carbons.

The acid reactants fall in two primary groups: (a) hydroxy aliphaticcarboxylic acids having 1-3 carboxy groups and l-2 hydroxy groups withthe general formula (HO) R(COOH) wherein R is a saturated aliphatichydrocarbon radical with 1-4 carbons, and (b) polycarboxy saturatedaliphatic acids with the general formula HOOCR -(COOH) where R is asaturated ether or hydrocarbon radical with 1-4 carbons. The hydroxygroups may be primary, secondary, or even tertiary hydroxy groups. Thecarboxy groups may be on either or both of the terminal carbons of thealiphatic chains of R or R and/or may be on intermediate carbons of thealiphatic chain of R or R Acids of the above character are citric acid,succinic acid, tricarballylic acid, lactic acid, tartaric acid,tartronic acid, malic acid, diglycollic acid, and the like.

The reaction products herein contemplated which are obtained withremoval of less than 1.0 mol of water per mol of acid such as citricacid, i.e., 0.5 mol up to about 1.0 mol of water per mol of acid(especially around 0.5 to 0.8 mol of water removed), are less preferredfrom the viewpoint of universal applicability in the treatment of {ahydrocarbon liquids herein contemplated than the reaction productsobtained with removal of about 1.0 to 3.0 mols of water per mol of acid.The former reaction products occasionally are insutliciently soluble ina particular hydrocarbon liquid to give them the optimumdepositinhibiting or anti-fouling properties whereas the latter reactionproducts have a better overall solubility in the various kinds of liquidhydrocarbons herein contemplated to at least the extent of solubilitysufficient to impart optimum deposit inhibition on heated metal surfacesin contact with the treated hydrocarbon liquid.

The reaction product which is most consistently successful in thereduction of tube deposits and improvement of filterability is thereaction product of 2-3 mols of the -tertiary-alkyl primary aminespreviously described with one mol of citric acid obtained in a reactionwith the removal of 1.53 mols of water. The critic acid is preferablyanhydrous, or at least substantially anhydrous.

The reaction products of the instant invention may be prepared by any ofseveral methods. They may be reacted at atmospheric pressure or undervacuum without a solvent. Alternatively, a high boiling solvent may beemployed to reduce the viscosity of the ultimate product and thusfacilitate agitation and mixing of the reactants. The solvent in thiscase has a boiling point high enough that it is not distilled off to anyappreciable extent during the reaction at the prevailing pressure.

Another method of preparation involves the use of a low boiling solvent,such as toluene, which forms an azeotropic mixture with the water ofreaction. The distillate is refluxed and the water separated from thelow boiling solvent before the latter is returned to the reactionmixture.

In all of the foregoing methods, the reactants are heated sufilcientlyhigh to distill off the water of reaction at the prevailing pressureconditions. In reactions at atmospheric pressure, the tertiary-alkylprimary amine and citric acid are mixed together in a vessel equippedwith an agitator and heating means and heated to a temperature betweenabout 110 C. and 160 C. for /2 to 2 /2 hours the time temperaturerelationship depending upon the amount of water of reaction to beremoved. The heating of the reactants is terminated when the desiredamount of water of reaction is removed-the latter being determined bycollecting and measuring the water distilled off. An alternative methodfor determining the end-point involves ascertaining of the acid numberof samples taken at periodic intervalsthe reaction being terminated whenthe approximate desired acid number is reached. In a preferred form ofthe invention, the reaction is terminated so as to obtain a producthaving an acid number, based on the active ingredients, in the range of65-90, preferably 7585. One preferred method at atmospheric pressureinvolves heating the amine to a temperature of 50 C.60 C. and adding thecitric acid slowly in increments. After all the citric acid is added thereactants are gradually heated to a temperature of 140 C.160 C. in aperiod of about one-half to one hour. The reaction mixture is held atthis temperature for an additional 1. /2 to 2 /2 hours. If desired, theproduct may be diluted with a suitable hydrocarbon solvent such as heavyaromatic petroleum oils, i.e., at least 50% aromatics, or xylene to thedesired concentration.

In a reaction under vacuum, the amine is vigorously stirred and thecitric acid is added in portions. The mixture is then rapidly heated.When the temperature is in the range of 100120 C., a full vacuum isslowly applied. The reaction is kept at this temperature for about /z2hours and is then cooled rapidly to 100 C. A suitable hydrocarbonsolvent is then added in an amount suflicient to provide the requiredconcentration.

When a high boiling solvent such as Stoddard Solvent or other commericalhigh boiling hydrocarbon solvent is employed, the amine and citric acidare mixed with the desired amount of solvent, and the mixture is heatedwith agitation in the manner previously described. The azeotropicdistillation method is carried out by mixing the amine and citric acidwith a low boiling solvent such as toluene in a reaction vessel equippedwith an agitator, condenser, and Barrett trap for separating the waterand solvent in the azeotropic distillate and the mixture is heated withagitation. The solvent begins to reflux, and refluxing is continued withthe removal of water from the azeotropic distillate until the desiredamount of water is removed.

The invention will be further understood from the following specificexamples and it will be understood that the invention is not limitedthereto.

EXAMPLE I Three mols of Primene JM-T and one mol of citric acid, alongwith 368 grams of Stoddard Solvent, are added to a reaction vesselequipped with an agitator, thermometer, Barrett trap and condenser. Themixture is heated until the temperature reaches C. at which point avacuum is applied. Distillation begins, and about three milliliter ofthe solvent is distilled over and collected. The temperature of thereaction mixture continues to rise and at about 126 C., the distillationbecomes more vigorous. The temperature remains constant thereafter atabout 124-126 C. During the reaction period, the temperature rises toabout C., and the reaction is stopped when 25.2 milliliters of waterhave distilled over. This amount of water is equivalent to 1.4 mols ofwater per mol of citric acid.

EXAMPLE II Primene JM-T and citric acid are reacted at a molar ratio of3:1, respectively, in a vessel identical with that described in ExampleI. The reaction mixture is heated and agitated and at 120 C. a vacuum isapplied. After a few minutes, distillation of the water begins. As thereaction proceeds, the reaction mixture begins to darken. Heating iscontinued until the temperature is in the range of 140l50 C. Thereaction is continued until about 1.8 mols of water per mol of citricacid are removed. Thereafter the heating is discontinued and thereaction product is diluted with a suitable hydrocarbon solvent to thedesired concentration.

EYAMPLE III Three mols of Primene JM-T are added to an open vessel, andthe amine is heated to a temperature between 50 and 60 C. One mol ofcitric acid is added portionwise to the amine. After all of the acid isadded, the temperature is raised and held within the range of C. Theproduct begins to darken at this temperature and after 2 /2 hours, anacid number is taken and found to be about 85. The reaction is thenstopped and the product was made up into a 75% solution in aromatichydrocarbon solvent and filtered through a filter cell.

EXAMPLE IV Equal mols of Primene 8l-R and citric acid are mixed with anamount of toluene equal to about twice the total weight of the amine andacid in a reaction vessel identical with that described in Example I.The mixture is stirred and heated. At about 110 C., the toluene beginsto reflux and when the water in the azeotropic distillate is removed thecolor of the reaction mixture changes from a light yellow to a darkbrown as the reaction nears completion. After three hours of refluxingabout 1.8 mols of water per mol of citric acid have been removed and nofurther distillation of water is noted. The temperature at this point isabout 112 C. and the reaction is stopped.

EXAMPLE V In an apparatus identical with that of Example I, Primene 8lRand citric acid at a molar ratio of 3:1, respectively, are mixed with anamount of toluene aps proximately equal to the total weight of the amineand acid. The reaction mixture is heated and stirred. At about 110 C.the toluene begins to reflux and the water is removed from theazeotropic distillate. When one mol of water per mol of the acid isremoved, the reaction is stopped-the temperature at this point beingabout 118 C.

EXAMPLE VI Four hundred fifty pounds of Primene 81-R is pumped into astainless steel kettle equipped with stirrer, heater and cooling coils.The amine is heated to 215 F., and 150 lbs. of citric acid is added infour portions over a period of 15 minutes. The exothermic reactioncauses the temperature to rise to about 270 F. in about /z hour. Coolingis applied to prevent further temperature rise, and the reaction mixtureis held at 260270 F. for two hours and then cooled.

The products produced in accordance with the foregoing reactions arebelieved to be amine salts of the acid with a portion of the salt groupsconverted to amide groups by the elimination of water of reaction. Thus,the resultant product is believed to contain both amine salt groups andamide groups.

While the foregoing portion of the disclosure relates primarily toreaction products of citric acid, the preferred acid for purposes of myinvention, other hydroxy-substituted, saturated aliphatic carboxylicacids or unsubstituted, saturated aliphatic polycarboxylic acids may beemployed without departing from the spirit of the invention. Examples ofsuch acids are succinic acid, tricarballylic acid, lactic acid, tartaricacid, tartronic acid, and rnalic acid. The foregoing acids, includingcitric acid, may be characterzed by the fact that the total offunctional groups, hydroxy and/ or carboxy groups, is at least two andnot more than four and that the acids have 36 carbons. In the case ofdicarboxy or monocarboxy acids, the amount of tertiary-alkyl primaryamine is reduced to two mols or one mol per mol of acid, respectively.

The anti-fouling additives, generally in diluted form in a hydrocarbonsolvent, are added and mixed with the petroluem hydrocarbon liquid inamounts generally in the range of about 25-500 p.p.m., the concentrationbeing calculated on the basis of the active ingredients. The quantityadded for optimum results will vary between types of petroleumhydrocarbon liquids and temperatures to which they are subjected in theparticular processing ope on- While the additives of the instantinvention may be employed with some success in many diflerent types ofpetroleum hydrocarbon liquids, including crude oil, gas oil, heavydistillate oils, etc., they are most outstanding as anti-fouling agentsand deposit inhibiting agents when used in light petroleum distillatessuch as naphthas, diesel oils, kerosene, light furnace oils and thelike. In general, these latter petroleum hydrocarbon liquids havedistillation end points beginning above that of gasoline up to petroleumhydrocarbon liquids having distillation end points at about 750 F. Inthe broad sense, the petroleum hydrocarbon liquids to which the presentinvention is applicable cover a range from the crude oil, includingreduced crudes, to petroleum distillates, straight run or cracked,having distillation end points above the distillation end point ofgasoline '(about 400 F.). In diesel oils, the additives of thisinvention are also beneficial in alleviating hot filter plugging andgumming of the diesel injector parts and other fuel handling parts of adiesel engine which become heated during the operation of the engine. Aminimum concentration of about 75 p.p.m. of additive is advisable forthis beneficial effect.

The following are formulations which may be added to petroleumhydrocarbon liquids for the purpose of inhibiting the deposit formingtendencies of these oils at elevated temperatures on heating surfaces.

6 Composition A Percent Reaction product of Primene JM-T and citric acidat a mol ratio of 3:1, 1.5 mol of water eliminated per mol of citricacid 75.5 Bronoco 365, an aromatic solvent 24.5

Composition B Reaction product of Primene 81-R and citric acid, molratio 3: 1, 0.5 mol of water eliminated per mol of citric acid 20 Heavyaromatic hydrocarbon solvent Composition C Reaction product of Primene81R and citric acid (procedure of Example VI) 20 Bronoco 365 80Composition D Reaction product of 3 mols of Primene 81-R and 1 mol ofcitric acid, 1 mol of water eliminated per mol of citric acid 20 Heavyaromatic solvent 80 Composition E Reaction product of 3 mols of Primene81-R and 1 mol of citric acid, 2 mols of water eliminated per mol ofcitric acid 20 Heavy aromatic solvent 80 The above compositions weretested in an apparatus of laboratory size designed for determining theanti-fouling or deposit inhibiting tendencies of anti-fouling agents. Inthe test, the particular oil or petroleum hydrocarbon liquid beingtested is preheated and aerated, if called for by test conditions, in afeed tank. Agitation is provided by an aerator or by a power drivenmixer. A receiver or waste tank is pressurized with nitrogen to thedesired test pressure by opening an automatic regulator until thecorrect pressure is obtained. The apparatus drain is opened and thereceiver valve and bleed valve are closed. Temperature and pressurebypass switches are turned on, and the prepared feed is pumped into aheat exchange pipe in the form of a loop by means of the injection pump.The pump heater is turned on if the feed viscosity justifies its use.

When the feed flows continuously from the drain, that is without airbubbles, a recycle pump is turned on. For a high pressure test, therecycle pump is set at maximum speed in order to facilitate the removalof air from the recirculation loop, a welded stainless steel pipe,diameter inch in the high pressure apparatus. The loops in the lowpressure apparatus is a 15", straight, black iron tube, 7 O.D., /2"I.D., with the remaining portion of the loop being A" pipe connected byfittings. When the flow of feed from the drain is once again continuous,the drain valve is closed, and the pressure in the apparatus builds upto the continued injection of fresh feed. When the pressure in theapparatus reaches the level established for the test, a receiver valveis opened rapidly. The nitrogen bleed valve on the waste tank is thencracked slightly to allow displacement of the nitrogen by the waste feedfrom the apparatus. A balance must be established between the nitrogenbleed rate and the incoming rates of nitrogen to the reciver plus thewaste petroleum fluid so that a steady pressure is held throughout thetest. Nitrogen is discharged from the waste tank at a rate in excess ofthe volume of fluid entering the tank. Constant pressure in the wastetank and heat exchange loop is maintained with an automatic regulatingvalve on the nitrogen supply pressure cylinder.

A recorder is turned and the safety bypass switches are turned off. Thepower to the heater, a Nichrome wire wound about the pipe and covered byinsulation, is then turned on with the rate being established at thedesired value by means of the voltmeter and ammeter readings andcontrolled by a powerstat. The rates are adjusted,

based on past experience with feeds of a similar nature, to give thedesired oil temperature for the test. Water is circulated through adouble pipe oil cooler for cooling the waste oil. At this point, therecycle pump in the high pressure test is gradually slowed down to arate predetermined for the test,

An equilibrium or steady-rate condition is reached when the oiltemperature levels off and does not rise or fall more than 3 degreesduring a half-hour period. The time required to reach equilibrium isusually two hours but may be somewhat more or less in the case ofnaphthas. The oil and wall temperature differences are determined everyhalf hour with thermocouples after equilibrium is established, and heattransfer coeflicients are calculated. The percentage drop in the heattransfer is then determined. The percentage drop for a blank run is usedas the standard of comparison in the evaluation of additives used withthe same hydrocarbon liquid in subsequent tests.

The results of tests with various petroleum hydrocar- '3Polydodecylbenzene sulfonic acid is a mixture of diand higherdodecylbenzene sulfonic acids.

Composition G Percent 5 Solution in a hydrocarbon solvent of reactionproduct of 3 mols Primene 81-R and one mol citric acid, 2 mols watereliminated per mol citric acid, active component 50 Completelyneutralized ethylene diamine salt of polydodecylbenzene sulfonic acid inhydrocarbon solvent, active component Composition H Solution inhydrocarbon solvent of the reaction product of 3 mols of Primene 81-Rand 1 mol citric acid, 0.5 mol water eliminated per mol citric acid, 20%active component 50 Solution in hydrocarbon solvent of completelyneutralized salt of ethylene diamine and polydodecylbon liquids arereported in the following table. benzene sulfonic acid, 45% activecomponent 50 TABLE I Wall Temp, F. H.T.O. (U) B.t.u. Percent PercentActive Duration Oil Temp. Hr. Ft. F. Reduction Reduction PetroleumLiquid Treatment Cone, of Test, at Equil. F. in U. in Fouling p.p.m.Hrs. Rate Equil. End Equil. End

1. Gas Oil Blank 5 442 683 746 108 88 18.5 Comp. A- 225 5 448 691 711110 101 8. 2 56 2. Gas 011 Blank 4 452 640 688 119 91 23 Comp. B 30 4373 568 580 116 108 7 3. Gas 0il Blank".-. 5 470 808 872 83 69 17 Comp.A 150 5 471 790 813 88 81 8 53 4. Topped San .loaquine Crude Blank 5 460616 655 180 139 23 Comp. A 150 5 467 632 659 170 143 15 8 31 5.Heavy-15% Coker Naphtha Blank 5 398 546 670 91 51 43 Comp. D- 34 5 404548 576 94 79 15 65 Comp. E 34 5 398 540 583 79 16 63 Comp. A 34 5 408540 549 102 99 4 92 nk 5 390 628 611 95 72 25 Comp. B 34 5 412 548 56506 88 68 Comp. B 55 5 406 652 580 93 87 6 5 74 6. West Texas naphtha,Blank 8 490 611 670 233 152 35 Panhandle naphtha, C0mp.A 150 8 485 605605 229 229 0 natural gasoline. 7. Virgin Naphtha Blank 6 395 486 543209 140 33 Comp. A 150 6 398 490 524 207 167 19 43 8. Platinum Reformerlank 5 431 558 613 198 137 32 N aphtha. Comp. A" 150 5 437 542 550 246217 12 62 Comp. E 150 5 441 540 542 254 249 2 94 9. Virgin NaphthatBlank 6 420 661 728 93 75 20 Comp. 13-- 26 6 430 666 682 95 93 2 5 8810. Gas oil Blank" 5 442 683 746 108 88 18 5 5 452 684 684 115 100 11.Gas Oil 1 5 442 683 746 108 88 18 5 5 453 684 696 115 109 4 9 75 12.Reduced Crude 5 517 778 818 93 82 13 5 532 782 804 97 93 4 1 67 13. 85%Heavy-15% Coker 5 390 528 611 95 72 25 Naphthafl 5 409 560 560 94 94 100m 150 p.s.i., 2 gal/hr. input, 1.7 ft./see. velocity, aerated. b 150p.s.i., 1 gal/hr. input, 1.7 itJsec. velocity, nonaerated. 150 p.s.i., 2gaL/hr. input, 1.7 it./sec. velocity, aerated. d 150 p.s.i., 2 gal/hr.input, 1.7 it./sec. velocity, aerated. 600 p.s.i., 1 gal/hr. input, 0.8it./sec. velocity, aerated. f 600 p.s.i., 2 gal/hr. input, 2.2 ftJsec.velocity, aerated. I; 600 p.s.i., 2 gal/hr. input, 2.2 ft./sec.velocity, aerated.

h 600 p.s.i., 1 gaL/hr. input, 2.2 ft./sec. velocity, aerated. 600p.s.i., 2 gal/hr. input, 0.8 it./sec. velocity, aerated.

i 150 p.s.i., l gal/hr. input, 1.4 it./sec. velocity, preheated to F.,nonaerated.

Good anti-fouling results have also been noted with anti-foulingcompositions comprising a mixture of the previously described tertiaryprimary alkyl amine-citric acid reaction products and aryl sulfonates orsulfonic acids, particularly alkyl-substituted benzene sulfonic acidsand salts thereof such as amine salts.

The following are examples of such compositions:

Composition K Solution in hydrocarbon solvent of reaction product 3 molsPrimene 81-R and 1 mol citric acid, 2 mols of water eliminated per molcitric acid, 20% active component 50 Solution in hydrocarbon solvent ofcompletely neutralized ethylene diamine salt of polydodecylbenzenesulfonic acid, 45 active component 50 This combination of chemicals hasbeen observed to 70 have good anti-fouling properties with several typesof petroleum hydrocarbon liquids. Results of some tests using thesecompounds is reported in Table I, supra.

The weight ratio of activecomponents in the above mixture (the weightratio of the tertiary-alkyl primary 5 aminecitric acid reaction productto the ethylene diamine- 9 polydodecylbenzene sulfonic acid salt) willordinarily fall within the range of 4:1 to about 1:10 for most effectiveresults. The active concentration of these two ingredients in thehydrocarbon liquid will ordinarily lie within the range of 10500 ppm.

The invention is hereby claimed as follows:

1. In the processing of normally liquid hydrocarbons of petroleum originin a petroleum refinery operation, the step of passing said normallyliquid hydrocarbon of petroleum origin during processing thereof in apetroleum refinery operation in contact with a heated surface in heatexchange relationship therewith, which liquid hydrocarbon contains asmall but sufficient amount to inhibit formation of deposits by saidliquid hydrocarbon on said heated surface of a reaction product preparedby heating with the removal of water of reaction citric acid and atertiary-alkyl primary amine of the formula:

wherein R and R are lower alkyl groups and R is an alkyl group having8-19 carbons, the molar ratio of amine to acid in the reaction mixturelying in the range of 13:l, respectively, until 0.5-3.0 mols of water ofreaction per mol of citric acid are removed from the reaction mixture.

2. In the processing of normally liquid hydrocarbons of petroleum originin a petroleum refinery operation, the steps comprising passing thenormally liquid hydrocarbon of petroleum origin during processingthereof in a pctroleum refinery operation in contact with a heatedsurface in heat exchange relationship therewith, and adding to saidliquid hydrocarbon prior to contact with said surface a small butsuflicient amount to inhibit formation of deposits originating from saidliquid hydrocarbon on said heated surface of a reaction product preparedby heating, with the removal of at least 0.5 mol of water of reactionper mol of an aliphatic acid containing at least two and not more thanfour functional groups selected from the group consisting of hydroxy andcarboxy groups and having 3-6 carbons, a tertiary-alkyl primary amine ofthe formula:

R1 R -(J-NH and said aliphatic acid wherein R and R are lower alkylgroups and R is an alkyl group having 8-19 carbons, the molar ratio ofamine to acid in the reaction mixture being in the range of 13 1,respectively.

3. The process of claim 2 wherein the acid is tricarballylic acid.

4. The process of claim 2 wherein the acid is tartaric acid.

5. The process of claim 2 wherein the acid is succinic acid.

References Cited by the Examiner UNITED STATES PATENTS 2,099,350 11/1937Stoesser 20848 2,347,527 4/ 1944 Vanderbuilt 20848 2,387,501 10/ 1945Dietrich.

2,493,715 1/ 1950 Christ 44-71 2,684,292 7/ 1954 Caron et al 44682,908,624 10/1959 Johnson et al. 20848 2,923,611 2/ 1960 Wieland 44723,035,907 5/1962 Halter 447l FOREIGN PATENTS 790,604 2/1958 GreatBritain.

DANIEL E. WYMAN, Primary Examiner.

1. IN THE PROCESSING OF NORMALLY LIQUID HYDROCARBONS OF PETROLEUM ORIGININ A PETROLEUM REFINERY OPERATION, THE STEP OF PASSING SAID NORMALLYLIQUID HYDROCARBON OF PETROLEUM ORIGIN DURING PROCESSING THEREOF IN APETROLEUM REFINERY OPERATION IN CONTACT WITH A HEATED SURFACE IN HEATEXCHANGE RELATIONSHIP THEREWITH, WHICH LIQUJID HYUDROCARBON CONTAINS ASMALL BUT SUFFICIENT AMOUNT TO INHIBIT FORMATION OF DEPOSITS BY SAIDLIQUID HYUDROCARBON ON SAID HEATED SURFACE OF A REACTION PRODUCTPREPARED BY HEATING WITH THE REMOVAL OF WATER OF REACTION CITRIC ACIDAND A TERTIARY-ALKYL PRIMARY AMINE OF THE FORMULA: